MR. W. CROOKES ON RADIANT MATTER SPECTROSCOPY. 
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164. Finally the calcium spectrum by itself was examined. It is continuous, with 
no break, lines, or bands in it. 
The Anomalous Line — 2693. 
V 
165. On several occasions I have spoken of an orange line, 2693, which by its 
brilliancy and sharpness is a prominent object in most of the samarium-yttrium 
spectra. With samaric sulphate it is exceedingly faint. With samaria containing 
5 per cent, of yttria it is very little brighter; with 10 per cent, of yttria it gains 
a little; with 15 per cent, it is brighter still, and with a mixture of 80 parts samaria 
and 20 parts yttria it is at its maximum intensity. It continues to be the most 
striking feature in the spectra of the various mixtures of samaria and yttria until the 
proportion becomes samaria 3, yttria 97, when it begins to get less bright, and only 
when pure yttria is reached does it altogether vanish. 
The accompanying diagram (fig. 22) shows the rise and fall in intensity of this 
bright line, with the proportions of samaria and yttria experimented on. 
Fig. 22. 
166. It is noteworthy that so long as this bright line is a component of the 
spectrum, the other bands manifest decidedly less intensity than they do in other 
phosphorescent spectra where this line is absent. Many of the bands usually present 
in the samaria and yttria spectra are also suppressed. The profound modification in 
the spectra of samaria and yttria developed by their mixture is, I believe, without 
precedent in spectrum analysis. The molecules of each earth, samaria and yttria, 
which separately are capable of vibrating rhythmically and of giving a characteristic 
phosphorescent spectrum, when mixed yield a spectrum approaching in character 
that of samaria or of yttria, according as one or other earth preponderates, and 
produce the dominant line 2693. 
167. In this and the former paper on Radiant Matter Spectroscopy, much stress 
has been laid on the sensitiveness of the Radiant Matter test for indicating the 
